html,body{height:100%;overflow:hidden}*{box-sizing:border-box}body{margin:0;padding:0;background:linear-gradient(135deg,#667eea,#764ba2);height:100vh;font-family:Segoe UI,Tahoma,Geneva,Verdana,sans-serif;overflow:hidden}button{border:none;outline:none;cursor:pointer}button:focus{outline:2px solid #2563eb;outline-offset:2px}button:disabled{cursor:not-allowed}